Ink jet head

ABSTRACT

When all metal plates for forming a passage unit of an ink jet head are bonded together by metal bonding, a top metal plate will warp, and an actuator unit cannot be fitted in a uniform manner to this warped top metal plate, and if the actuator units are not fitted in a uniform manner to the top metal plate, a uniform amount of ink cannot be discharged from nozzles of the ink jet head. To deal with this, metal diffusion bonding of the metal plates is performed without the top metal plate being included therein, and the top metal plate is then caused to adhere by means of adhesive. There is thus no warping of the top metal plate, and consequently the actuator units can be fitted in a uniform manner to the top metal plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2004-380147, filed on Dec. 28, 2004, the contents of which are herebyincorporated by reference into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet head and a method ofmanufacturing the ink jet head.

2. Description of the Related Art

A certain type ink jet head is manufactured by fixing a passage unit andan actuator unit.

The passage unit is provided with at least one common passage, aplurality of branching passages, a plurality of pressure chambers, and aplurality of nozzles. Ink supplied from the exterior of the passage unitis received in the common passage. The plurality of branching passagesbranch from the common passage. Each of the pressure chambers is formedpart-way along one corresponding branching passage. Each of the nozzlescommunicates with an end part of one corresponding branching passage,and opens to the exterior of the passage unit. There is an equal numberof branching passages, pressure chambers and nozzles.

The passage unit is composed of a stack of a plurality of metal plates.Penetrating holes, grooves, etc., are formed in each of the metal platesto be stacked. The common passage, branching passages, pressurechambers, and nozzles are formed by stacking the metal plates.

The actuator unit is provided with a plurality of actuators. There is anequal number of actuators and pressure chambers. Each of the actuatorscan be controlled independently.

The actuator unit is fixed to a top metal plate of the passage unit. Thepositions in which the actuators of the actuator unit are disposed, andthe positions in which the pressure chambers of the passage unit aredisposed are adjusted such that each actuator is coupled with acorresponding pressure chamber when the actuator unit is fixed to thetop metal plate of the passage unit.

When one actuator is activated, the pressure increases within thepressure chamber that corresponds thereto, and ink is discharged fromthe nozzle communicating with this pressure chamber. The nozzle fromwhich the ink will be discharged can be chosen by choosing whichactuator to activate. The timing at which the ink will be dischargedfrom the nozzle can be chosen by choosing the timing at which theactuator will be activated.

In order to obtain the above phenomenon, the actuator and thecorresponding pressure chamber must have a positional relationship suchthat, when the actuator unit is fixed to the top metal plate of thepassage unit, this positional relationship allows the actuator toincrease the pressure within the corresponding pressure chamber when theactuator is activated.

One type of passage unit has holes formed in its top face. Each of holeshas a bottom. When the actuator unit is fixed to the top face of thepassage unit, each of the holes is covered by the actuator unit. Thesecavities form the pressure chambers. A positional relationship can beobtained such that, when an actuator is selected and activated, thepressure is increased within the pressure chamber corresponding to thatactuator. With this type of passage unit, the top metal plate isprovided with a plurality of penetrating holes, for forming pressurechambers.

In another type of passage unit, holes that have a bottom and form thepressure chambers are covered by a vibrating plate. The vibrating plateis a thin plate that flexibly deforms. In this case, as well, apositional relationship can be obtained such that, when an actuator isselected and activated, the pressure is increased within the pressurechamber corresponding to that actuator. With this type of passage unit,the top metal plate of the passage unit is the vibrating plate and has aflat surface.

When the ink jet head is to be manufactured, the passage unit and theactuator unit are manufactured separately. The passage unit and theactuator unit are then fixed.

The passage unit is manufactured by stacking the plurality of metalplates, as described above, and then bonding together the stacked metalplates. In order to do this, a stack of all metal plates that comprisesthe passage unit is provided, and this stack is heated under pressure tobond all the metal plates at one time. When the stacked metal plates areheated under pressure, the metal plates are bonded stably together bymetal diffusion bonding. The passage unit can be manufacturedefficiently by bonding all the metal plates that comprise the passageunit at one time.

BRIEF SUMMARY OF THE INVENTION

As described above, the passage unit can be manufactured efficientlywhen all the metal plates for forming the passage unit are bonded at onetime. However, the present inventors discovered that minute warping ofthe top metal plate occurs when the stacked metal plates are bonded bybeing heated under pressure. When there is minute warping of the topmetal plate, the actuator unit does not adhere in a uniform manner tothe top metal plate when the actuator unit is to be fitted thereto. Inthis case, the actuator unit efficiently increases the pressure withinthe pressure chambers in the places where the actuator unit fits well,and the appropriate amount of ink is discharged from the nozzlescommunicating with those pressure chambers. However, the actuator unitdoes not increase the pressure sufficiently within the pressure chambersin the places where the actuator unit does not fit well, and a smalleramount of ink is discharged from the nozzles communicating with thosepressure chambers. As a result, the amount of ink discharged from thenozzles of the ink jet head is not uniform. In this case, there is aproblem that print quality grows worse when printing is to be performedby this ink jet head.

The present invention teaches a method of completing a passage unit inwhich minute warping does not occur in a top metal plate of the passageunit.

In the present invention, a method is taught of completing an ink jethead by causing an actuator unit to fit in a uniform manner to a flattop face of a passage unit.

In the present invention, an ink jet head is taught in which a passageunit and an actuator unit fit together in a uniform manner and in whichthere is little discrepancy in the amount of ink being discharged fromnozzles.

A method of manufacturing an ink jet head according to this inventionincludes the following steps; preparing a stack of a plurality of metalplates; heating the stack under pressure to bond the plurality of metalplates and produce an incomplete passage unit; causing a top metal plateto adhere to the incomplete passage unit by means of an adhesive tocomplete the passage unit; and fixing an actuator unit to the top metalplate of the completed passage unit.

In the above method, the step is not performed of bonding all the metalplates for forming the passage unit at one time. Instead, the metalplates are bonded in a state in which at least the top metal plate isnot included. Since the top metal plate is not bonded in this step, thepassage unit is not complete. The incomplete passage unit is made first,and then an adhesive is used to cause the top metal plate to adhere tothe incomplete passage unit.

With this method, there is no metal diffusion bonding with respect tothe top metal plate, and consequently minute warping thereof does notoccur. Since there is no minute warping of the top metal plate, theactuator unit can fit in a uniform manner with the passage unit. As aresult, the nozzles of the ink jet head discharge a uniform amount ofink, and high printing quality is possible.

In the conventional method of manufacturing the ink jet head, all themetal plates for forming the passage unit are bonded at one time tocomplete the passage unit. However, in the method of manufacturing theink jet head of the present invention, the manufacturing process isdivided into two steps: the step of manufacturing the incomplete passageunit by metal diffusion bonding, and the step of causing the top metalplate to adhere to the incomplete passage unit. Although increasing thenumber of steps is undesirable from the viewpoint of productionefficiency, it allows a high quality ink jet head to be manufactured.

In the step of manufacturing the incomplete passage unit, all the metalplates with the exception of the top metal plate may be bonded.Alternatively, all the metal plates with the exception of the top metalplate and a bottom metal plate may be bonded. If the bottom metal platealso needs to be extremely flat, both the top metal plate and the bottommetal plate may be caused to adhere to the incomplete passage unit.

As described above, the number of steps is increased in the above methodof manufacturing the ink jet head. However, this problem can be solvedby performing a preferred manufacturing method in which the top metalplate is caused to adhere to the passage unit simultaneously with theactuator unit being fixed to the top metal plate.

With this method, there is no increase in the number of steps formanufacturing the ink jet head, and a high quality ink jet head can bemanufactured.

The present invention presents a novel ink jet head. The ink jet head ofthe present invention is composed of a passage unit and an actuatorunit. The passage unit comprises a top metal plate and a plurality oflower metal plates. The top metal plate and the lower metal plates arestacked. The top metal plate is adhered to the lower metal plates bymeans of adhesive, and the lower metal plates are bonded together bymetal diffusion bonding. The actuator unit is fixed to the top metalplate of the passage unit.

With the ink jet head that has this configuration, the actuator unit andthe top metal plate fit together in a uniform manner. As a result, thereis a uniform amount of ink discharged from the nozzles of the ink jethead, and high quality printing can be achieved.

A passage unit of another type of the present invention includes a topmetal plate, a plurality of intermediate metal plates, and a bottommetal plate. The top metal plate, intermediate metal plates, and bottommetal plate are stacked. The top metal plate and the intermediate metalplates are adhered by means of adhesive, and the intermediate metalplates are bonded together by metal diffusion bonding. The intermediatemetal plates and the bottom metal plate are adhered by means ofadhesive.

With this ink jet head, the top metal plate and the bottom metal plateare both extremely flat, and high quality printing is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an ink jet head module of a firstembodiment.

FIG. 2 shows a cross-sectional view along the line II-II of FIG. 1.

FIG. 3 shows a plan view of an ink jet head.

FIG. 4 shows an expanded view of a region A of FIG. 3.

FIG. 5 is a disassembled perspective view showing a stacked state ofmetal plates that form a passage unit.

FIG. 6 shows a cross-sectional view along the line VI-VI of FIG. 4.

FIG. 7( a) shows a partially expanded cross-sectional view of anactuator unit, and FIG. 7( b) shows a plan view of an individualelectrode and a land.

FIG. 8 shows steps for manufacturing the ink jet head of the firstembodiment.

FIG. 9 is an explanatory view showing a metal diffusion bonding step.

FIG. 10 is a cross-sectional view equivalent to FIG. 6 of an ink jethead of a second embodiment.

FIG. 11 shows steps for manufacturing the ink jet head of the secondembodiment.

FIG. 12 is an explanatory view showing a metal diffusion bonding step ofthe second embodiment.

FIG. 13 is a front view of an ink jet head.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will now be describedwith reference to the drawings. FIG. 1 shows a schematic perspectiveview of ink jet head module 1 of a first embodiment of the presentinvention. FIG. 2 shows a cross-sectional view along the line II-II ofFIG. 1 Ink jet head module 1 is incorporated in a printing device (anink jet printer in the present embodiment), and prints on a paper bydischarging ink towards the paper being conveyed in a secondaryoperating direction (the y direction in FIG. 1). Ink jet head module 1extends in a widthwise direction of the paper (the x direction of FIG.1), and can print by discharging ink onto desired positions in thewidthwise direction of the paper.

Ink jet head module 1 is composed of ink jet head 70 for discharging inkonto the paper, base block 71 for supplying ink to ink jet head 70,holder 72 to which ink jet head 70 and base block 71 are fixed, andwirings 90 (see FIG. 2) for supplying electrical signals to ink jet head70.

Holder 72 is provided with grip portion 72 a, and a pair of flatplate-shaped protruding portions 72 b that extend in a perpendiculardirection from grip portion 72 a. As shown in FIG. 2, a lower face ofgrip portion 72 a is formed in a concave shape. Base block 71 is fixedwithin the concave part of grip portion 72 a. Ink jet head 70 is fixedto a lower side of base block 71. Wirings 90 are disposed on both outerside faces of two protruding portions 72 b.

Base block 71 is fixed within the concave part formed at the lower faceof grip portion 72 a. Base block 71 is formed from stainless steel, andtwo ink reservoirs 3 are formed within base block 71. Ink reservoirs 3are substantially rectangular parallelepiped shaped hollow regions thatare formed along the lengthwise direction (the x direction of FIG. 1) ofbase block 71. Base block 71 has a passage (not shown) for leading inksupplied from an ink tank disposed at the exterior to ink reservoirs 3.Ten penetrating holes 3 b are formed in lower face 73 of base block 71.Ten penetrating holes 3 b communicate with ink reservoirs 3. Neighboringportion 73 a of each of penetrating holes 3 b protrudes downwards belowother parts of lower face 73.

Ink jet head 70 is fixed to base block 71 such that the upper face ofink jet head 70 faces lower face 73 of base block 71. Ten penetratingholes 3 b are formed in positions facing ten openings 5 b formed in inkjet head 70 (to be described). Neighboring portions 73 a that protrudedownward near penetrating holes 3 b of base block 71 make contact withportions neighboring openings 5 b of ink jet head 70.

A plurality of manifolds 5 (to be described) are formed within ink jethead 70. Openings 5 b of ink jet head 70 communicate with manifolds 5.The ink supplied from the ink tank is supplied to manifolds 5 of ink jethead 70 via ink reservoirs 3, penetrating holes 3 b, and openings 5 b.

Ink jet head 70 is fixed to lower face 73 of base block 71. FIG. 13shows a front view of ink jet head 70. As shown in FIG. 13, ink jet head70 is composed of one passage unit 4 and four actuator units 21.

FIG. 5 is a disassembled perspective view of ink jet head 70. As shownin FIG. 5, passage unit 4 is composed of metal plates 22˜29 and nozzleplate 30 that have been stacked. Metal plates 22˜29 and nozzle plate 30are metal plates formed from stainless steel or the like. That is,nozzle plate 30 is also a type of metal plate. A plurality ofpenetrating holes are formed in each of metal plates 22˜29 and nozzleplate 30. Although this is not shown, a water-repellent layer consistingof fluorinated resin is formed on a lower face of nozzle plate 30. Thiswater-repellent layer is readily affected by heat, and will be damagedif heated above a predetermined temperature. Four actuator units 21 arefixed to an upper face of metal plate 22.

FIG. 3 shows a plan view of ink jet head 70. As shown in FIG. 3, tenmanifolds 5 are formed from the penetrating holes formed in metal plates22˜29 and nozzle plate 30 within passage unit 4. One end of each ofmanifolds 5 opens into the upper face of ink jet head 70 (i.e. the upperface of metal plate 22) at a location that does not interfere withactuator units 21. The other end of each of manifolds 5 branches to formsub-manifolds 5 a. As described above, ink is supplied from inkreservoirs 3 of base block 71 to openings 5 b of manifolds 5. The inksupplied to manifolds 5 is supplied into sub-manifolds 5 a. Manifolds 5have a wide cross-sectional area up until sub-manifolds 5 a, andpressure is the same in each part thereof, this essentially forming onecommon ink passage.

FIG. 6 is a cross-sectional view of ink jet head 70, and is an enlargedschematic view of one ink discharging path (a branching passage that hasbranched into a pressure chamber and a nozzle). As shown in FIG. 6,branching passage 32 is formed from the penetrating holes formed inmetal plates 22˜29 and nozzle plate 30 within passage unit 4. One end ofeach of branching passages 32 is connected with sub-manifolds 5 a (thecommon passage), and the other end thereof is connected withcorresponding nozzle 8. Branching passages 32 receive the ink suppliedfrom sub-manifolds 5 a, and lead this ink to nozzles 8. Nozzles 8 openinto the lower face of nozzle plate 30, and discharge the ink suppliedfrom branching passages 32. Pressure chamber 10 is formed part-way alongbranching passage 32. Pressure chamber 10 is formed from a penetratinghole formed in metal plate 22, and is covered by actuator unit 21.Pressure chamber 10 is filled with the ink that was supplied from submanifold 5 a via an upstream portion of branching passage 32. Aperture12 is formed in branching passage 32 at the side upstream from pressurechamber 10.

As shown in FIG. 7( a), actuator units 21 are fixed to the upper face oftop metal plate 22 of passage unit 4. Each actuator units 21 is composedof four ceramic plates 41˜44. Ceramic plates 41˜44 are formed fromferroelectric ceramic material. In the present embodiment, they areformed from lead zirconate titanate (PZT) ceramic material. Ceramicplates 41˜44 are polarized in their direction of thickness. Further, thethickness of each of ceramic plates is 15 μm.

Individual electrodes 35 are formed on an upper face of ceramic plate 41at locations directly above pressure chambers 10 of passage unit 4.Individual electrodes 35 are formed from Ag-Pd metal. Further, as shownin FIG. 7( b), Individual electrodes 35 are substantially diamondshaped, and one portion thereof extends outwards. Land 36 is formed atthis extending portion. Lands 36 are circular, have a diameter ofapproximately 160 μm, and are composed of gold that contains glass flit.Lands 36 are electrically connected with wiring pattern of FPC 50 (to bedescribed).

Common electrode 34 is formed across approximately the entire facebetween ceramic plate 41 and ceramic plate 42. Common electrode 34 isgrounded at a location not shown in the figures. Common electrode 34 isformed from Ag-Pd metal.

FIG. 4 shows an expanded view of a passage of a region A of FIG. 3. Thepassage within passage unit 4 is shown by a solid line. As shown in FIG.4, a plurality of branching passages 32 is formed within passage unit 4.These branching passages 32 extend from sub-manifolds 5 a to nozzles 8via apertures 12 and pressure chambers 10. Branching passages 32 areformed in a matrix shape. Manifolds 5 and sub-manifolds 5 a are formedwithin passage unit 4 for supplying ink to matrix-shaped branchingpassages 32. Further, the reference numbers 35 in FIG. 4 representindividual electrodes 35 of actuator units 21. That is, individualelectrodes 35 are formed at locations directly above each pressurechambers 10 on an upper face of actuator unit 21. In order for this tobe shown more clearly, only some of individual electrodes 35 have beenshown in FIG. 4. However, individual electrodes 35 are actually formeddirectly above all pressure chambers 10.

One actuator is formed from one individual electrode 35, portion ofceramic plates 41, 42, 43, and 44 facing individual electrode 35, andcommon electrode 34 facing individual electrode 35. Each actuator unit21 includes a plurality of actuators.

As shown in FIG. 2, each of wirings 90 has FPC 50 (Flexible PrintedCircuit), driver IC 80, base 81, and heat sink 82. FPC 50 is disposedalong holder 72 via resilient member 83 such as a sponge or the like. Alower edge of FPC 50 extends into a space formed between lower face 73of base block 71 and the upper face of ink jet head 70, and is fixed tothe upper face of ink jet head 70. More precisely, the lower edge of FPC50 is fixed to the upper face of actuator unit 21. A plurality ofwirings are formed in FPC 50, and a terminal is formed at a lower edgeof each wiring. A plurality of lands 36 is formed on the upper face ofactuator unit 21. The distribution pattern of the terminals of FPC 50 isidentical with the distribution pattern of lands 36 of actuator unit 21,and when the lower edge of FPC 50 is fixed to the upper face of actuatorunit 21, the wirings are connected with corresponding lands 36. DriverIC 80 is disposed part-way along FPC 50. Each output terminal of driverIC 80 is electrically connected with the wiring formed on FPC 50. Heatsink 82 is fixed to a surface of driver IC 80. Heat sink 82 prevents atemperature rise of driver IC 80. Sealing member 84 is provided aroundheat sink 82 to prevent dust or ink within ink jet head module 1 fromentering therein.

Base 81 is fixed to the outer faces of two protruding portions 72 b ofholder 72. Base 81 is electrically connected with the wiring near anupper edge of FPC 50. That is, base 81, driver IC 80 and actuator unit21 are electrically connected by FPC 50.

When base 81 sends an electrical signal to driver IC 80, this causesdriver IC 80 to send an electrical signal to actuator unit 21. Actuatorunit 21 is driven by the electrical signal sent from driver IC 80.Driver IC 80 selects the wiring that will carry current, and selectsindividual electrodes 35 to which electric potential will be applied.

The operation of ink jet head module 1 at the time of printing will nowbe described. During printing, the paper is conveyed in a secondaryscanning direction (the y direction in FIG. 1) by the ink jet printer.The paper passes under a lower face of ink jet head module 1. The lengthof ink jet head module 1 is identical with the width of the paper. Basedon the information of the design to be printed, the ink jet printerselects individual electrodes 35 to which electric potential will beapplied, and controls the timing at which the electric potential will beapplied. For the former case, the nozzles from which ink will bedischarged are selected and thereby the points at which the ink will bedischarged are selected with respect to the widthwise direction of thepaper. For the latter case, the points at which the ink will bedischarged are selected with respect to the lengthwise direction of thepaper. Specifically, an electrical signal is sent from base 81 to driverIC 80. Driver IC 80 sends an electrical signal to individual electrodes35 of actuator unit 21 based on the electrical signal that has beenreceived. The signal sent by driver IC 80 causes the electric potentialof individual electrodes 35 to be positive.

Usually, the electric potential of individual electrodes 35 of actuatorunit 21 is maintained at approximately 0 V. Further, common electrode 34is grounded, and consequently individual electrodes 35 and commonelectrode 34 have approximately the same electric potential. In theaforementioned process, driver IC 80 causes the electric potential ofindividual electrodes 35 to be positive, whereupon an electric field iscreated between individual electrodes 35 and common electrode 34.Further, ceramic plates 41˜44 are formed from ferroelectric material,and the direction of polarization thereof is the direction of thicknessof ceramic plates 41˜44. As a result, the direction of the electricfield created between individual electrodes 35 and the common electrode34 is parallel with the direction of polarization of ceramic plate 41.Consequently, electrostriction effects caused by the electric fieldcause ceramic plate 41 to contract in a direction at a right angle toits direction of polarization. By contrast, ceramic plates 42˜44 are notaffected by the electric field, and consequently do not contractspontaneously. Ceramic plates 41˜44 thus deform so as to protrude towardpassage unit 4 (unimorph deformation) at the area surrounding individualelectrode 35 to which the electric potential has been applied. When theactuator deforms, the volume decreases of pressure chamber 10 thatcorresponds thereto. When the volume of pressure chamber 10 decreases,the pressure of the ink increases within the pressure chamber 10, andthis ink is discharged onto the paper from nozzle 8 that communicateswith this pressure chamber.

Driver IC 80 returns individual electrode 35 to its original electricpotential, whereupon the electric field that was created betweenindividual electrode 35 and common electrode 34 is eliminated. When theelectric field is eliminated, ceramic plate 41 that had contractedreturns to its original state, and then the actuator that had deformedso as to protrude toward passage unit 4 returns to its original state.Thereupon, the volume of pressure chamber 10 corresponding theretoreturns to its original state, whereupon ink is attracted into pressurechamber 10 from branching passage 32 at aperture 12 side thatcorresponds thereto, and pressure chamber 10 is thus refilled.

As described above, driver IC 80 selects individual electrodes 35 andsends the electrical signal to selected individual electrodes 35, thuscausing the ink to be discharged from selected nozzles 8 that correspondto selected individual electrode 35. Driver IC 80 sends the electricalsignals to selected individual electrodes 35 with the requisite timingbased on the information of the design to be printed and on the positioninformation of ink jet head module 1. As a result, ink is dischargedwith the requisite timing from selected nozzles 8, and the design isprinted.

Next, a method of manufacturing ink jet head 70 of the presentembodiment will be described with reference to FIG. 8.

In S10, the penetrating holes are formed in all of metal plates 22˜30(this including top metal plate 22 and nozzle plate 30 that forms thebottom metal plate) for forming passage unit 4. The penetrating holesare formed by etching. Further, the water-repellent layer is formed onthe lower face of nozzle plate 30.

In S11, of metal plates 22˜30 that have had the penetrating holes formedtherein, metal plates 23˜29 are stacked together to form a stack. Topmetal plate 22 and the bottom metal plate 30 (the nozzle plate) are notincluded in this stack. The stack of metal plates 23˜29 are heated underpressure. Then, adjacent metal plates are bonded together by metaldiffusion bonding, thus unifying the stack. FIG. 9 is an explanatoryview showing Si 1 of FIG. 8. As shown in FIG. 9, metal plates 23˜29 arestacked and are then gripped between a pair of pressing jigs 62 and 63formed within a furnace. Once metal plates 23˜29 are gripped betweenpressing jigs 62 and 63, pressure within the furnace is reduced and anapproximate vacuum state is formed. Thereupon, the furnace is heated toabout 1000° C. while pressure is being applied to metal plates 23˜29between pressing jigs 62 and 63. Metal plates 23˜29 are maintained for aconstant time in this state of being heated under pressure, thus causingthe metal diffusion bonding of the adjacent metal plates of metal plates23˜29. Once the metal diffusion bonding of metal plates 23˜29 has beenperformed, incomplete passage unit 60 has been manufactured.

In S12 of FIG. 8, top metal plate 22 (the cavity plate) and bottom metalplate 30 (the nozzle plate) are caused to adhere by means of adhesive toincomplete passage unit 60. That is, a lower face of top metal plate 22is caused to adhere to an upper face of metal plate 23, and an upperface of bottom metal plate 30 is caused to adhere to a lower face ofmetal plate 29. Passage unit 4 is thus completed.

In S13 of FIG. 8, actuator unit 21 is manufactured by being baked. Thatis, individual electrodes 35 are formed on an upper face of a greensheet that is the material of ceramic plate 41, and common electrode 34is formed on a lower face of the green sheet. When individual electrodes35 and common electrode 34 have been formed on the green sheet that isthe material of ceramic plate 41, this green sheet and green sheets thatform the material of ceramic plates 42˜44 are stacked. When the greensheets have been stacked, these green sheets are heated, and aremaintained in the heated state for a constant time. The green sheetsthat have been hardened by baking form ceramic plates 41˜44. Further,ceramic plates 41˜44 each bond with the adjacent ceramic plates, therebycompleting actuator unit 21.

In S14 of FIG. 8, four completed actuator units 21 are caused by meansof adhesive to adhere to completed passage unit 4. That is, lower facesof actuator units 21 are caused to adhere to the upper face of passageunit 4. When actuator units 21 have been caused to adhere to passageunit 4, ink jet head 70 is complete.

With the aforementioned manufacturing method, top metal plate 22 iscaused by means of adhesive to adhere to metal plate 23 at the upperside of incomplete passage unit 60. That is, there is no metal diffusionbonding of top metal plate 22, and consequently warping thereof does notoccur. When there is no warping of top metal plate 22, actuator units 21can, by being adhered, be made to fit in a uniform manner with top metalplate 22, and consequently a uniform amount of ink is discharged fromnozzles 8. As a result, high quality printing is possible.

As described above, the water-repellent layer of nozzle plate 30 isreadily affected by heat, and consequently this water-repellent layerwould be damaged if nozzle plate 30 were heated at the time of metaldiffusion bonding. However, with the aforementioned manufacturingmethod, nozzle plate 30 does not undergo metal diffusion bonding. Sincenozzle plate 30 is not heated, there is no damage to the water-repellentlayer formed on the lower face of nozzle plate 30.

A complicated step is usually required to form the water-repellent layeron the completed ink jet head. In the present embodiment, after thewater-repellent layer has been formed on the lower face of nozzle plate30, and consequently complicated steps are not required to completeinkjet head 70. It is relatively easy to form the water-repellent layeron nozzle plate 30 that exists as a single unit.

The manufacturing method of the present embodiment can be used inmanufacturing a passage unit comprising a vibrating plate. Below, inkjet head 101 of a second embodiment will be described. Parts that havethe same configuration as the first embodiment have the same referencenumbers applied thereto, and a description thereof will be omitted whereappropriate.

As shown in FIG. 10, ink jet head 101 of the second embodiment alsoconsists of passage unit 4 and actuator unit 91.

Passage unit 4 of the second embodiment is a stacked structurecomprising vibrating plate 92 and metal plates 22˜30. Like the firstembodiment, passages are formed within passage unit 4 from metal plates22˜29 and nozzle plate 30. In passage unit 4 of the second embodiment,openings of pressure chambers 10 formed in metal plate 22 are covered byvibrating plate 92. Actuator unit 91 is fixed to an upper face ofvibrating plate 92.

Vibrating plate 92 is a thin metal (stainless steel) plate that readilydeforms when an actuator deforms. Vibrating plate 92 does not intervenewith the phenomenon of the pressure change in pressure chamber 10 causedby the deformation of the actuator. Vibrating plate 92 is the top metalplate of passage unit 4 of the second embodiment.

Vibrating plate 92 is grounded at a location not shown in the figures.Further, although this is not shown, penetrating holes are formed invibrating plate 92, these penetrating holes communicating with inkreservoirs 3 and manifolds 5.

Actuator unit 91 is a structure in which individual electrodes 95 areformed on an upper face of ceramic plate 93. As in the first embodiment,individual electrodes 95 are formed directly above pressure chambers 10.Further, one portion of each of individual electrodes 95 extendsoutwards, and land 96 is formed at each of these extending portions.

With ink jet head 101 of the second embodiment, vibrating plate 44operates as a common electrode. When individual electrode 95 is causedto have an electric potential positive, an electric field createdbetween individual electrode 95 and vibrating plate 44 causes ceramicplate 93 to contract in a direction at a right angle to its direction ofpolarization. By contrast, vibrating plate 44 does not contractspontaneously. Thereupon, ceramic plate 93 and vibrating plate 44deform, in the area surrounding individual electrode 95 to which thepositive electric potential has been applied, so as to protrude towardpressure chamber 10. The volume of pressure chamber 10 thus decreases.When the volume of pressure chamber 10 decreases, the pressure of theink within pressure chamber 10 increases, and this ink is dischargedonto the paper from nozzle 8. Consequently, as in the first embodiment,the design can be printed on the paper. In this case, as well, oneactuator is formed by individual electrode 95, ceramic plate 93 in thearea facing individual electrode 95, and vibrating plate 44 of this samearea. Actuator unit 91 is provided with the same number of actuators asthe number of pressure chambers 10.

The operation of ink jet head 101 at the time of printing will now bedescribed. At the time of printing, driver IC 80 sends an electricalsignal to selected individual electrodes 95. This electrical signalcauses the electric potential of selected individual electrodes 95 to bepositive.

Usually, the electric potential of individual electrodes 95 ismaintained at approximately 0 V. Further, vibrating plate 92 isgrounded, and consequently individual electrodes 95 and vibrating plate92 have approximately the same electric potential. When driver IC 80causes the electric potential of selected individual electrodes 95 to bepositive, an electric field is created between selected individualelectrodes 95 and vibrating plate 92. Thereupon, electrostrictioneffects caused by the electric field cause ceramic plate 93 to contractin a direction at a right angle to its direction of polarization. Bycontrast, vibrating plate 92 does not contract spontaneously. Actuatorunit 91 and vibrating plate 92 therefore deform (unimorph deformation),in the area surrounding selected individual electrode 95 to which thepositive electric potential has been applied, so as to protrude towardpressure chamber 10. When vibrating plate 92 deforms, the volume ofpressure chamber 10 decreases, the pressure of the ink within pressurechamber 10 increases, and this ink is discharged onto the paper fromnozzle 8.

Driver IC 80 returns individual electrode 95 to its original electricpotential, whereupon actuator unit 91 and vibrating plate 92 return totheir original state. Thereupon, the volume of pressure chamber 10returns to its original state, and consequently pressure chamber 10 isrefilled with ink.

As with ink jet head 70 of first embodiment, ink jet head 101 of thesecond embodiment allows the paper to printed.

Next, steps for manufacturing ink jet head 101 will be described withreference to FIG. 11.

In S20, the penetrating holes are formed in all of the metal plates forforming passage unit 4, i.e. vibrating plate 92, metal plates 22˜29, andnozzle plate 30. The penetrating holes are formed by etching. Further, awater-repellent layer is formed on a lower face of nozzle plate 30.

In S21, eight metal plates 22˜29 are stacked together to form a stack.Top metal plate 92 (the vibrating plate) and bottom metal plate 30 (thenozzle plate) are not included in this stack. The stack of eight metalplates 22˜29 are bonded together by metal diffusion bonding. FIG. 12 isan explanatory view showing S21. As shown in FIG. 12, metal plates 22˜29are stacked and are then gripped between a pair of pressing jigs 62 and63 formed within a furnace. Once metal plates 22˜29 are gripped betweenpressing jigs 62 and 63, pressure within the furnace is reduced and anapproximate vacuum state is formed. Thereupon, the furnace is heated toabout 1000° C. while pressure is being applied to metal plates 22˜29between pressing jigs 62 and 63. Metal plates 22˜29 are maintained for aconstant time in this state of being heated under pressure, thus causingthe metal diffusion bonding of adjacent metal plates 22˜29. Incompletepassage unit 111 is thus manufactured.

In S22 of FIG. 11, vibrating plate 92 and nozzle plate 30 are caused toadhere by means of adhesive to incomplete passage unit 111. That is, alower face of vibrating plate 92 is caused to adhere to an upper face ofmetal plate 22, and an upper face of nozzle plate 30 is caused to adhereto a lower face of metal plate 29. Passage unit 4 is thus completed.

In S23 of FIG. 11, actuator units 91 that have already been produced arecaused by means of adhesive to adhere to top metal plate 92 (thevibrating plate) of passage unit 4. That is, lower faces of actuatorunits 91 are caused to adhere to the upper face of passage unit 4. Whenactuator units 91 have been caused to adhere to passage unit 4, ink jethead 101 is complete.

With the aforementioned manufacturing method, vibrating plate 92 iscaused by means of adhesive to adhere to adjacent metal plate 22. Thatis, there is no metal diffusion bonding of vibrating plate 92, andconsequently warping thereof does not occur. When there is no warping ofvibrating plate 92, actuator units 91 can be made to fit in a uniformmanner with vibrating plate 92, and consequently a uniform amount of inkis discharged from nozzles 8. As a result, high quality printing ispossible.

Further, with the aforementioned manufacturing method, there is no metaldiffusion bonding of nozzle plate 30. That is, since nozzle plate 30 isnot heated, there is no damage to the water-repellent layer formed onthe lower face of nozzle plate 30.

Representative embodiments have been described above. However, thepresent invention is not restricted to the embodiments described above.Various improvements and transformations are possible without deviatingfrom the purpose of the present invention.

For example, in the above embodiments, the top metal plate and theactuator unit were caused to adhere to the incomplete passage unit inseparate steps. However, the top metal plate and the actuator unit mayequally well be made to adhere simultaneously. With this type ofmanufacturing method, the ink jet head can be manufactured moreefficiently.

In the above embodiments, the nozzle plate was caused to adhere by meansof adhesive. However, the nozzle plate may equally well undergo metaldiffusion bonding together with the other metal plates. In the casewhere the water-repellent layer is not formed on the nozzle plate, thereis no problem in the nozzle plate undergoing metal diffusion bonding.

Further, in the above embodiments, all of the metal plates were bondedby metal diffusion bonding with the exception of the top metal plate andthe bottom metal plate. However, this manufacturing method is notnecessarily required. For example, if the second from top metal plate isbonded by metal diffusion bonding and there is warping of this metalplate, thus causing warping of the top metal plate located above thisplate, the second from top metal plate and the top metal plate may becaused to adhere by means of adhesive to the incomplete passage unitthat was manufactured using metal diffusion bonding. In this case, boththe second from top metal plate and the top metal plate can be assessedas the top metal plate.

In the above embodiments, the actuator unit deformed so as to protrudetoward the pressure chamber when the electrical signal was sent to theindividual electrode. However, the actuator unit may equally wellprotrude away from the pressure chamber. With this type ofconfiguration, as well, the ink can be discharged from the nozzle.

In the above embodiments, the individual electrodes were formed on theupper face of the actuator unit. However, the individual electrodes mayequally well be formed within the actuator unit, and the commonelectrode may be formed on the upper face of the actuator unit. Withthis type of configuration, as well, the actuators within the actuatorunit can be made to deform independently by sending the electricalsignals to the individual electrodes.

In the above embodiments, a description was given of an actuator thatincreases the pressure within the pressure chamber by means ofdeforming. However, the actuator may equally well be an actuator thatincreases this pressure by heating the ink within the pressure chamber.

As described above, in one form of a manufacturing method of the ink jethead of the present invention, the top metal plate made to adhere to theincomplete passage unit is a vibrating plate. The vibrating plate is ametal plate that vibrates while the actuator unit is activated.

In one form of a manufacturing method of the ink jet head of the presentinvention, the top metal plate made to adhere to the incomplete passageunit is the cavity plate. A plurality of penetrating holes are formed inthe cavity plate, and these penetrating holes are covered by theactuator unit.

In one form of a manufacturing method of the ink jet head of the presentinvention, the bottom metal plate made to adhere to the incompletepassage unit is the nozzle plate. The nozzle plate has a plurality ofpenetrating holes that comprise the nozzles formed therein.

1. An ink jet head, comprising: a passage unit comprising a top metalplate and lower metal plates stacked together, the top metal plate andthe lower metal plates being adhered by means of an adhesive, and thelower metal plates being bonded together by metal diffusion bonding, andan actuator unit fixed to the top metal plate of the passage unit.
 2. Anink jet head as defined in claim 1, wherein the top metal plate is avibrating plate that vibrates while the actuator unit is activated. 3.An ink jet head as defined in claim 1, wherein the top metal plate has aplurality of penetrating holes that are closed by the actuator unit. 4.An ink jet head as defined in claim 1, wherein the passage unit has abottom metal plate having a plurality of penetrating holes for forming aplurality of nozzles.
 5. An ink jet head, comprising: a passage unitcomprising a top metal plate, intermediate metal plates and a bottommetal plate stacked together, the top metal plate and the intermediatemetal plates being adhered by means of an adhesive, the intermediatemetal plates being bonded together by metal diffusion bonding, and theintermediate metal plates and the bottom metal plate being adhered bymeans of an adhesive, and an actuator unit fixed to the top metal plateof the passage unit.